Firefox: Not lightweight at all, bad support from authors and generally a memory hog. Not that Chrome and Opera are any lighter (in fact Chrome is WORSE than Firefox at the moment).
Gnome-Mplayer: Maybe since it only needs Mplayer and codecs to work. Not Totem unless you actively want to drag half of GNOME with it.
PCMANFM: Legacy doesn't work without HAL and the current version is heavier (dependency and resources wise) than XFCE4. We might as well just use XFCE4 instead. Spacefm is pretty much dead too.
Xarchiver: While it's my favorite archive extraction program, it hasn't been updated in years, so it lacks proper support for 7zip and the new xz formats.

about your "vote to decide which program"
InternetBrowser, ImageEditing, Office, Player, VideoEditing, none by default but a repo where I can choose the one I like
(eg. I use Midori, so i dont want FF build in by default)
Maybe I'm the only one but I like to have a small, basic system
and then I decide what to add to it.
You can find a "full featured oob distro" on every corner; but not a small one.
cheers

hihi , yes I still do. By now, I know 5 newbies who give up after a black screen. I don't like to feel boring to linux newcomers when I say : " yes but .. bla bla bla .." ;) . A kind of Slitaz "Mint" or "XP" flavor (with stable packages) could be a nice idea as long as it might be possible to strip off all the unecessary during the wizard-configurator session.

I dream to have the choice to decide myself which program I want for each task that I need to complete.

My dream:
I start SliTaz from an USB key (or a frugal install), a minimalist iso with only Xorg, Gtk, Openbox, LXDE. No apps.

Then I load Tazweb, to display an App Center, a page listing software categories like Internet, Graphics, Office.. you know this stuff. I select which apps I want to install, push Enter and my selection of packages is installed from the internet, or even better from a cache located on the USB Key.

Almost how I use SliTaz these days, except I do not have an App Center, I do all this stuff by hand in CLI mode.

Backports is a good idea.
It can include every packages that can be compiled with the stable SliTaz toolchain.
Except the toolchain.
So we can have packages uptodate with security fix and missing fonctionnalities.